122 



BACTERIOLOGY 



lower tip of the stopper to the level of the opening, 0. The 

 horizontal limb is deep where it joins the vertical, but gradually 

 becomes shallow and ends about one-quarter the way around the 

 stopper. This groove serves for passage of the gas from the inner 

 tube BC, to the opening 0, and" thus to the 

 outer chamber D, and by rotating the stopper, 

 the amount of gas flowing through this 

 passage may be reduced to any desired point. 

 The outlet tube, H, leads from the chamber D 

 to the burner connection. 



The capillary, EF, leads to a bulb of suffi- 

 cient size; the larger the more sensitive the 

 instrument. Either the large bulb with in- 

 side capillary, J, to be filled with mercury 

 and toluol, or the smaller simple bulb for 

 mercury alone may be used. A side arm is 

 attached to one side of the capillary EF, for 

 conveniently controlling the height of the 

 mercury column. Either the curved capillary 

 tube with stopcock and a cup on the end, or 

 the simple tube with metal screw cemented 

 in, may be used here, according to the pur- 

 pose which the regularor is to serve. These 

 parts are similar to those of Novy's modi- 

 fication of the Reichert regulator. 



To fill the instrument, the air is partly 

 driven out by heating the bulb 'and then the 

 desired liquid is drawn in by cooling, re- 

 peating the heating and cooling until the 

 instrument is full of the liquid. For the small bulb, mercury is 

 always used alone. The large bulb, on the other hand, is filled 

 first with' either ether, alcohol or toluol, and then part of this 

 liquid is forced out by heat and replaced with mercury so that 

 the capillary EF, the bulb at its lower end, and a small part of the 

 large bulb |J, are occupied by the mercury. Ether may be used 



Pig. so. — Mac Neal 

 gas-regulator. 



